Search

Deviations from the Paschen's law in air and nitrogen are investigated for gaps from 100 nm to 10 μm, by using a high precision electrode positioning system. The deviation is observed when electrode gaps are smaller than 4 μm at atmospheric pressure. At distances lower than 1 μm, a nearly constant average breakdown field of 350 V/μm is evidenced in both gases with Au and Ru electrodes. A metallic plasma initiated by field emission from the cathode can explain the reduction of the breakdown voltage at such low gaps. In ambient air, the existence of a pre-breakdown current is also evidenced, probably due to the presence of water adsorbed on electrodes.

The generation, growth, and collapse of vapor bubbles in purified cyclohexane under a high divergent electric field was studied as a function of hydrostatic pressure (105–1.2×107 Pa). In these experimental conditions a very fast and localized energy injection (10−10–10−8 J) occurs as a consequence of electron avalanches, and the liquid is raised to a supercritical state. Below the critical pressure of the liquid, a vapor bubble is created. In this paper we present a time‐resolved optical study of its dynamics which is shown to be controlled by inertial forces. The transition to a streamer phenomenon is also investigated and discussed.